1. Field of the Invention
The present invention relates to a bending transducer for generating electrical energy from mechanical deformations.
2. Description of Related Art
Piezoelectric transducer mechanisms are used in the area of sensor and actuator systems in particular. For converting the mechanical stresses occurring in deformed structures, a piezoelectric element is generally coupled directly to a support element, i.e., a support structure, whereby the support structure may also be a second piezoelectric element (known as a piezoelectric bimorph). The piezoelectric element here has two electrodes for supplying and removing electrical charges to and from an electronic interface. The electrodes here are generally designed to be on the opposite sides of the piezoelectric element, which is usually flat.
For example, published German patent application document DE 10 2005 062 872 A1 describes a device for detecting the rolling motion of a vehicle wheel in which a piezoelectric element is contacted on a chip carrier via the electrodes formed on its opposite sides, its upper electrode being contacted via a wire bond, and the chip carrier, including the piezoelectric element and the wire bond, is cast into a mold compound. In such sensors for measuring accelerations, e.g., vibrations, reliable contacting is thus possible with little complexity.
Moreover, piezoelectric materials are increasingly used for generating electrical energy from energies of the surroundings, in particular vibrations and deformations; this is also referred to as energy harvesting. Bending deformations of the piezoelectric element are enabled here which result in clearly higher energy generation than, for example, the mechanical strains of a piezoelectric element cast into a mold compound, as allowed by published German patent application document DE 10 2005 062 872 A1.
In bending transducers in which the support structure and the piezoelectric element are fixedly restrained, electrical contacting may be implemented in a relatively simple manner since the piezoelectric element is fixedly connected to a housing. The use of a sufficiently large-surface and thus expensive piezoelectric element is generally required for such configurations, the areas of the piezoelectric element at the housing connection being exposed to only relatively minor changes in mechanical stress.
If the piezoelectric element is not fixedly restrained, contacting generally takes place via flexible wire connections. However, these wire connections are also exposed to the mechanical stresses that occur and have, with respect to the repeated deformations, only limited reliability.